Python - 访问嵌套在字典中的值 [英] Python - accessing values nested within dictionaries

问题描述

我有一本字典，其中包含字典，也可能包含字典，例如

  dictionary = {'ID'：0001 ，'名称'：'组成名称'，'交易'：
 {'交易参考'：'a1'，'交易详情'：
 {'Bill To'：'abc' ''''''''''''Widget A'
 ...} ...} ...} 
  

目前，我正在拆包以获得ID 001的条例草案，交易参考a1如下：

  if dictionary ['ID'] == 001：
 transactions = dictionary ['Transactions'] 
如果事务['Transaction Ref'] =='a1'：
 transaction_details = transactions ['Transaction Details'] 
 bill_to = transaction_details ['Bill To'] 
  

$ b $我不禁想到这是有点笨拙，特别是最后两个李nes - 我觉得像以下这样的东西应该有效：

  bill_to =交易['交易详情'] [' Bill To'] 
  

是否有更简单的方法来深入嵌套字典，而无需打包到临时变量？

解决方案

  bill_to =交易['交易详情'] ['Bill To' ] 
  

实际工作。 事务['Transaction Details'] 是一个表示 dict 的表达式，因此您可以在其中进行查找。对于实际的方案，我宁愿使用OO方法来嵌套嵌套的dict。 collections.namedtuple 特别适用于快速设置一大堆只包含数据的类（而不是自己的行为）。

$ b有一个注意事项：在某些设置中，您可能需要在执行查找时捕获 KeyError ，而在此设置中，这也很难说明哪个字典查找失败：

  try：
 bill_to = transactions ['Transaction Details'] ['Bill To'] 
除了KeyError：
＃两个查找中哪一个失败？ 
＃我们不知道除非我们检查异常; 
＃但是在两个步骤中更容易执行查找和错误处理
  

I have a dictionary which contains dictionaries, which may also contain dictionaries, e.g.

dictionary = {'ID': 0001, 'Name': 'made up name', 'Transactions':
               {'Transaction Ref': 'a1', 'Transaction Details':
                  {'Bill To': 'abc', 'Ship To': 'def', 'Product': 'Widget A'
                      ...} ...} ... }

Currently I'm unpacking to get the 'Bill To' for ID 001, 'Transaction Ref' a1 as follows:

if dictionary['ID'] == 001:
    transactions = dictionary['Transactions']
        if transactions['Transaction Ref'] == 'a1':
            transaction_details = transactions['Transaction Details']
            bill_to = transaction_details['Bill To']

I can't help but think this is is a little clunky, especially the last two lines - I feel like something along the lines of the following should work:

bill_to = transactions['Transaction Details']['Bill To']

Is there a simpler approach for drilling down into nested dictionaries without having to unpack into interim variables?

解决方案

bill_to = transactions['Transaction Details']['Bill To']

actually works. transactions['Transaction Details'] is an expression denoting a dict, so you can do lookup in it. For practical programs, I would prefer an OO approach to nested dicts, though. collections.namedtuple is particularly useful for quickly setting up a bunch of classes that only contain data (and no behavior of their own).

There's one caveat: in some settings, you might want to catch KeyError when doing lookups, and in this setting, that works too, it's hard to tell which dictionary lookup failed:

try:
    bill_to = transactions['Transaction Details']['Bill To']
except KeyError:
    # which of the two lookups failed?
    # we don't know unless we inspect the exception;
    # but it's easier to do the lookup and error handling in two steps

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